Field of Invention
The auxiliary device of screwdriver refers to an add-on structure arranged on a screwdriver. The screwdriver refers to a tool to drive nut bolts or screws. The auxiliary device comprises a magnetic element thereon to allow the screwdriver to automatically magnetically catch the head of the nut bolt, such that the screwdriver can stably attract and keep the head of the nut bolt in order to steadily drive the nut bolt.
Description of Related Arts
A prior conventional structure having the following patent numbers: DE1022230, DE102013110284, and U.S. Pat. No. 5,101,698, is an auxiliary device for a screwdriver to keep the position of the nut bolt, which is to set an auxiliary device on an end of the screwdriver and to use that auxiliary device to keep and clasp the nut bolt, so as to keep the head of the nut bolt in position on the driving end of the screwdriver. By such way of axis retaining, the position of the nut bolt can be kept when the screwdriver is axially rotating, which will not hinder the screwdriver from driving the nut bolt. However, the components of these prior structures are complex, which requires higher labor cost on the assembling. Besides, the patent of number U.S. Pat. No. 5,101,698 developed “Screw head depth limiter,” which is a simple component that is able to limit the depth of the head of the nut bolt in reaching into the workpiece, but unable to provide the function of keep the position of the head of the nut bolt. In addition, FIGS. 8 and 9 show a prior invention of the present inventor. Referring to FIG. 8, a screwdriver 6′ and a jacket 8 was disclosed. The screwdriver 6′ is a rod 61′ extending to form a driving portion 62′, wherein there is a recess 63′ set at where the rod 61′ is close to the driving portion 62′. Also, the jacket 8 is a hollow cylinder which inner margin has a annular bearing rib 81. The axial section of the bearing rib 81 is a pyramid-shape that slightly slants oppositely. The jacket 8 is embedded on the recess 63′ by means of the bearing rib 81. It has to be mentioned specifically that the jacket 8 has no expanding flexibility, so it requires mechanic pressure to push the jacket 8 onto the screwdriver 6′ by constraint until the jacket 8 is pushed to the rod 61′ of the screwdriver 6′ and the bearing rib 81 is embedded on the recess 63′. Moreover, when the jacket 8 is sleeved on the screwdriver 6′, it can not be taken off from the screwdriver 6′ easily.
FIG. 9 discloses another implementation of the jacket 9. The inner margin of the jacket 9 further has a plurality of spaced and separated ribs 91. The rib 91 has a slope 92 that is triangular in a axially sectional view. The ribs 91 can help the jacket 9 to be pushed and sleeve onto the screwdriver smoothly.
Both of the above two types of jacket 8 and 9 do not have expanding and restoring flexible structure. In other words, both the jackets 8 and 9 require mechanic compelling force to be push onto the screwdriver 6′ and the ribs 81 and 91 thereof make the pivoting of the jackets 8 and 9 on the screwdriver 6′ unsmoothly.